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Towards relieving center segregation in twin-roll cast Al-Mg-Si-Cu strips by controlling the thermal-mechanical process

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Journal of Materials Science & Technology 2023年第17期148卷 31-40页

作者： Shao-You Zhang Xuan wang yuan-Ting Mo Cheng wang Tuo Cheng Orest Ivasishin Pin-Kui Ma hui-yuan wang Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Nanling CampusJilin UniversityChangchun 130025China International Center of Future Science Jilin UniversityChangchun 130012China

Serious center segregation greatly limits the application of twin-roll casting(TRC)technology for produc-ing 6xxx alloy ***,Al-0.9Mg-0.6Si-0.2Cu-0.1Fe(wt.%,6061)strips with different thicknesses were fabricated by TRC,and we found that the center segregation was well relieved with the thick-ness increased from 3 mm to 4 *** reveal the mechanisms of mitigation of center segregation in the 4 mm strip,various techniques including solidification simulation,crystallographic calculation,elec-tron backscatter diffraction(EBSD),and electron probe micro-analyzer(EPMA)were *** re-sults disclosed that the Fe-containing phase in the 3 mm strip wasπ-AlFeMgSi,while the counterpart in the 4 mm strip wasα-***α-AlFeSi could serve as nucleation substrates for Mg_(2)Si and Q-AlCuMgSi phases,thus promoting the uniform distribution of elements and preventing the accumulation of phases in the center *** matching planes between theα-AlFeSi and Q/Mg_(2)Si were exam-ined as:(1120)_(α-AlFeSi)//(0001)_(Q),(0001)_(α-AlFeSi)//(110)_(Mg2Si),and(1120)_(α-AlFeSi)//(110)_(Mg2Si).Meanwhile,the smaller roll separating force during the TRC process in the 4 mm strip could weaken the force-induced liquid flow behavior in the semi-solid region,which is the other reason for the alleviation of center *** to the elimination of the center segregation,a more excellent fracture elongation was achieved in the as-homogenized 4 mm strip(∼29%)compared with the counterpart of the 3 mm strip(∼20%).This work may provide a strategy to eliminate the center segregation,thus further promoting the application of TRC process and producing high-performance Al alloy strips efficiently.

关键词： Aluminum alloy Twin-roll casting Center segregation Fe-containing phase Nucleation substrate

Discovery of Balmer broad absorption lines in the quasar LBQS 1206+1052

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Research in Astronomy and Astrophysics 2012年第4期12卷 369-382页

作者： Tuo Ji Ting-Gui wang Hong-Yan Zhou hui-yuan wang Key Laboratory for Research in Galaxies and Cosmology University of Science and Technology of China （USTC） Hefei 230026 China Center for Astrophysics USTC Hefei 230026 China Polar Research Institute of China Shanghai 200136 China

We report the discovery of Balmer broad absorption lines （BALs） in the quasar LBQS 1206＋1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides the Mg II λλ2796, 2803 doublet, BALs are also detected in the He I＊ multiplet at λλ2946, 3189, 3889 A arising from the metastable helium 2 3 S level, and in Hα and Hβ from the excited hydrogen H I＊ n = 2 level, which are rarely seen in quasar spectra. We identify two components in the BAL troughs of v ～ 2000 km s 1 width： One component shows an identical profile in H I＊, He I＊ and Mg II with its centroid blueshifted by v c ≈ 726 km s-1 . The other component is detected in He I＊ and Mg II with v c ≈ 1412 km s-1 . We estimate the column densities of H I＊, He I＊, and Mg II, and compare them with possible level population mechanisms. Our results favor the scenario that the Balmer BALs originate in a partially ionized region with a column density of N H ～ 10 21 10 22 cm-2 for an electron density of n e ～ 10 6 10 8 cm-3 via Lyα resonant scattering pumping. The harsh conditions needed may help to explain the rarity of Balmer absorption line systems in quasar spectra. With an i-band PSF magnitude of 16.50, LBQS 1206＋1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness and unique spectral properties make LBQS 1206＋1052 a promising candidate for followup high-resolution spectroscopy, multi-band observations, and long-term monitoring.

关键词： galaxies active -- quasar absorption lines -- quasar individual (LBQS1206+1052)

Recent progress in self-repairing coatings for corrosion protection on magnesium alloys and perspective of porous solids as novel carrier and barrier

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Journal of Magnesium and Alloys 2023年第10期11卷 3585-3608页

作者： Yajie Yang Yufei wang Mei-Xuan Li Tianshuai wang Dawei wang Cheng wang Min Zha hui-yuan wang Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Jilin UniversityChangchun 130022China School of Materials Science and Engineering Hebei University of TechnologyTianjin 300130China International Center of Future Science Jilin UniversityChangchun 130012China

Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.

关键词： Mg alloys Coatings Self-repairing Corrosion protection Porous solids

Simultaneous refinement of α-Mg grains and β-Mg_(17)Al_(12) in Mg-Al based alloys via heterogeneous nucleation on Al_(8)Mn_(4)Sm

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Journal of Magnesium and Alloys 2023年第1期11卷 348-360页

作者： Jun-Chen Chen Mei-Xuan Li Zhi-Yang Yu Zhao-yuan Meng Cheng wang Zhi-Zheng Yang hui-yuan wang State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130012PR China Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Jilin UniversityNanling CampusNo.5988 Renmin StreetChangchun 130025PR China International Center of Future Science Jilin UniversityChangchun 130012PR China

Due to the significant differences in the formation temperature and crystal structure between the primaryα-Mg and eutecticβ-Mg_(17)Al_(12),it is a great challenge to achieve simultaneous refinement of the primary and eutectic phases in Mg-Al based alloys via heterogeneous ***,we found that theα-Mg andβ-Mg_(17)Al_(12) in the AZ80 alloy can be simultaneously refined after 0.2 wt.%Sm addition,with the grain size decreasing from∼217±15μm to∼170±10μm and theβ-Mg_(17)Al_(12) morphology changing from a typical continuous network to a nod-like or spherical *** simultaneous refinement mechanism is investigated through solidification simulation,transmission electron microscopy(TEM),and differential thermal analysis(DTA).In the AZ80-0.2Sm alloy,many Al8Mn4Sm particles can be observed near the center of theα-Mg grains or inside theβ-Mg_(17)Al_(12).Crystallographic calculations further reveal that the Al8Mn4Sm has good crystallographic matching with both theα-Mg andβ-Mg_(17)Al_(12),so it possesses the potency to serve as heterogeneous nucleation sites for both *** promoted heterogeneous nucleation on the Al8Mn4Sm decreases the undercooling required by the nucleation of the primary and eutectic phases,which enhances the heterogeneous nucleation rate,thus causing the simultaneous refinement of theα-Mg andβ-Mg_(17)Al_(12).The orientation relationships between the Al8Mn4Sm and Mg/Mg_(17)Al_(12) are identified,which are[1210]_(Mg)//[010]_(Al8Mn4Sm),(1010)_(Mg)//(301)_(Al8Mn4Sm) and[112]_(Mg_(17)Al_(12))//[010]_(Al8Mn4Sm),(110)_(Mg_(17)Al_(12))//(301)_(Al8Mn4Sm),***,the refinement of theβ-Mg_(17)Al_(12) accelerates its dissolution during the solution treatment,which is beneficial for cost saving in industrial *** Al8Mn4RE compounds such as Al8Mn4Y might have the same positive effect on the simultaneous refinement due to the similar physicochemical properties of rare earth *** work not only proves the po

关键词： Magnesium alloys Microstructure refinement Primaryα-Mg Eutecticβ-Mg_(17)Al_(12) Rare earth Heterogeneous nucleation

Alloying design and microstructural control strategies towards developing Mg alloys with enhanced ductility

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Journal of Magnesium and Alloys 2022年第5期10卷 1191-1206页

作者： Zhong-Zheng Jin Min Zha Si-Qing wang Shi-Chao wang Cheng wang Hai-Long Jia hui-yuan wang Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Nanling CampusJilin UniversityNo.5988 Renmin StreetChangchun 130025China International Center of Future Science Jilin UniversityChangchun 130012China State Key Laboratory of Superhard Materials Jilin UniversityChangchun 130012China

Nowadays,magnesium(Mg)alloys are promising lightweight structural materials,especially in transportation and aerospace fields,due to their inherent low density and high specific *** of the high-strength Mg alloys exhibit poor formability and ductility at room temperature,which limit their wide ***,by proper alloying design and/or delicate microstructural control,some newly developed Mg alloys,including rare-earth(RE)and RE-free ones,show enhanced ductility without significant loss of *** identify the critical reasons,recent researches on ductile Mg alloys have been reviewed from the aspects of alloying design strategies and microstructural control via advanced processing ***,some outlooks on enhanced ductility of Mg alloys are suggested,*** the beneficial effect of solute atoms,introducing second phase particles,tailoring bimodal-grained structures,introducing pre-twinning structures,*** current research progresses in alloying design and/or novel microstructural control have shed some lights on designing and producing Mg alloys with enhanced ductility.

关键词： Mg alloys Alloying Microstructure Ductility Strength

Effect of Microstructures and Textures on Different Surfaces on Corrosion Behavior of an as-Extruded ATZ411 Magnesium Alloy Sheet

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Acta Metallurgica Sinica(English Letters) 2021年第8期34卷 1029-1041页

作者： Shuai Zhang Bao-Chang Liu Mei-Xuan Li hui-yuan wang Yin-Long Ma Key Laboratory of Drilling and Exploitation Technology in Complex Conditions of Ministry of Land and Resources College of Construction EngineeringJilin UniversityNo.938 Ximinzhu StreetChangchun 130026China Key Laboratory of Automobile Materials of Ministry of Education School of Materials Science and EngineeringJilin UniversityNanling CampusNo.5988 Renmin StreetChangchun 130025China

The effect of textures on different surfaces of an as-extruded Mg-4 Al-1 Sn-1 Zn(ATZ411) alloy sheet on its corrosion behavior was systematically investigated. The microstructure was examined by optical/scanning electron microscopy. The texture was characterized by X-ray diffraction and electron backscatter diffraction. The corrosion performance was evaluated by immersion tests, electrochemical measurements, and corrosion morphology observation. The results showed that there were obvious differences in the corrosion morphology and corrosion resistance on different surfaces. The surface perpendicular to extrusion direction had better corrosion resistance and more uniform corrosion damage than that perpendicular to the normal direction and that perpendicular to the transverse direction in 3.5 wt% NaCl solution. The corrosion morphology was mainly determined by the distribution of the second phase and fine-grained regions. The corrosion rate was more related to the overall texture.

关键词： Corrosion behavior Micro-galvanic Magnesium alloys Texture Extrusion

Discovery of a variable broad absorption line in the BL Lac object PKS B0138-097

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Research in Astronomy and Astrophysics 2011年第10期11卷 1163-1170页

作者： Shao-Hua Zhang hui-yuan wang Hong-Yan Zhou Ting-Gui wang Peng Jiang Key Laboratory for Researches in Galaxies and Cosmology Department of Astronomy University of Sciences and Technology of China Chinese Academy of Sciences Hefei 230026China Polar Research Institute of China Jinqiao Rd. 451 Shanghai 200136 China

We report the discovery of a broad absorption line （BAL） of - 10^4 km s^-1 in width in the previously known BL Lac object PKS 0138-097, which we tentatively identified as an Mg II BAL. This is the first detection of a BAL, which is sometimes seen in powerful quasars with high accretion rates, in a BL Lac object. The BAL was clearly detected in its spectra spanning two epochs at a high luminosity state taken in the Sloan Digital Sky Survey （SDSS）, while it disappeared in three SDSS spectra taken at a low luminosity state. The BAL and its variability pattern were also found in its historical multi-epoch spectra in the literature, but have been overlooked previously. In its high resolution radio maps, PKS 0138-097 shows a core plus a one- sided parsec-scale jet. The BAL variability can be interpreted as follows： The optical emission is dominated by the core in a high state and by the jet in a low state and the BAL material is located between the core and jet so that the BAL appears only when the core is shining. Our discovery suggests that outflows may also be produced in active galactic nuclei at a low accreting state.

关键词： galaxies active -- galaxies absorption lines -- BL Lacertae objects individual (PKS 0138-097)

A Study on the Impact of Chemical Structure on the Evolution of Aggregate Structure in Fiber-shaped High Density Polyethylene Vitrimer

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Chinese Journal of Polymer Science 2024年第10期42卷 1557-1565,I0013页

作者： Bing wang yuan-Chu Gao Hai wang hui Niu State Key Laboratory of Fine Chemicals School of Chemical EngineeringDalian University of TechnologyDalian116024China

Vitrimers have emerged as a prominent research area in the field of polymer *** of the studies have focused on synthesizing polymers with versatile dynamic crosslinking structures,while the impact of chemical structure on aggregate structure of vitrimers,particularly during polymer processing,remains insufficiently *** present study employed commercial maleic anhydride-grafted-high density polyethylene(M-g-HDPE)as the matrix and hexanediol as the crosslinker to facilely obtain fiber-shaped HDPE vitrimers through a reaction extrusion and post-drawing *** chemical structure characterization,morphology observation,thermal and mechanical properties investigation,as well as aggregate structure analysis,this work revealed the influence of dynamic bonds on the formation of aggregate structures during fiber-shaped vitrimers processing.A small amount of dynamic bonds in HDPE restricts the motion of PE chain during melt-extruding and post-drawing,resulting in a lower orientation of the PE ***,lamellar growth and fibril formation during post-drawing at high temperature are enhanced to some extent due to the competition between dynamic bond and chain *** uneven morphology of fibershaped HDPE vitrimers can be attributed to the stronger elastic effect brought by dynamic bonding,which plays a more dominant role in determining the mechanical properties of fiber-shaped vitrimers compared to aggregate *** Vitrimers have emerged as a prominent research area in the field of polymer *** of the studies have focused on synthesizing polymers with versatile dynamic crosslinking structures,while the impact of chemical structure on aggregate structure of vitrimers,particularly during polymer processing,remains insufficiently *** present study employed commercial maleic anhydride-grafted-high density polyethylene(M-g-HDPE)as the matrix and hexanediol as the crosslinker to facilely obtain fiber-shap

关键词： High density polyethylene vitrimer Fiber-shaped Aggregate structures Transesterification reaction

A corrosion-resistant and age-hardenable Mg-Al-Mn-Ca-Ce dilute alloy with fine-grained structure processed by controlled rolling

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Journal of Materials Science & Technology 2023年第32期163卷 223-236页

作者： Jia-Sheng Li Mei-Xuan Li Zhen-Ming Hua yuan-Ting Mo Kai Guan Min Zha Yipeng Gao hui-yuan wang Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Nanling CampusJilin UniversityChangchun 130025China State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130012China International Center of Future Science Jilin UniversityChangchun 130012China

Low strength and poor corrosion resistance are two long-standing bottlenecks with dilute Mg ***,we report that the corrosion resistance of Mg-0.6Al-0.5Mn-0.2Ca(wt.%)alloy sheet can be significantly improved by micro-alloying with 0.3 wt.%Ce,and the strength can be considerably augmented after aging *** optimization of strength,ductility,and corrosion resistance is difficult due to the inherent trade-off in Mg ***,our aged Mg-0.6Al-0.5Mn-0.2Ca-0.3Ce alloy features with yield strength(YS)of∼194 MPa,ultimate tensile strength(UTS)of∼265 MPa,elongation to failure(EF)of∼17.2%,and corrosion rate(CR)of 2.2 mm y^(−1),the combination of which exhibits competitive advantage over other comparative dilute Mg *** is found that Ce addition decreases the activity of cathodic phases,inhibits detrimental effects of Fe impurities,and forms a protective Ce-containing surface *** high strength stems from the precipitation of ordered Guinier-Preston(G.P.)zones dispersed in uniform fine grains with an average grain size of∼8.2μ*** atomic-scale *** result in a noticeable age hardening response but do not act as crack initiation and propagation site,so our alloy also performs satisfactory *** work sheds light on the design and fabrication of strong,ductile,and corrosion-resistant dilute magnesium alloys to be used in electronic products and automotive bodies.

关键词： Magnesium alloy Micro-alloying Aging G.P.zones Mechanical property Corrosion